Modern large-scale commercial bakeries of the type utilized in the production of bread, sandwich buns, and similar dough products are frequently equipped with continuous proofing and baking apparatus. In the operation of a continuous proofer and/or oven, dough to be baked is received in bakery pans. The bakery pans are transported on grids which are supported on the links of a continuous chain. A drive mechanism actuates the chain to transport the bakery pans and the dough contained therein through a proofer wherein the dough is allowed to rise and/or through an oven wherein the dough is baked.
FIGS. 1, 2, and 3 illustrate a link 20 of the type comprising a prior art conveyor chain utilized in continuous proofing and baking apparatus. Each link 20 of the conveyor chain includes a first connection member 22, a second connection member 24, and a pair of spaced, parallel plates 26. The first connection member 22 of a particular link 20 is connected to the second connection member 24 of the next preceding link in the chain by a pin 28 (FIG. 3) which facilitates pivotal movement between adjacent links in the nominally vertical plane. The plates 26 are connected to the first connection member 22 and to the second connection member 24 by pins 30 which facilitate relative pivotal movement between adjacent links in the nominally horizontal plane.
The first connection member 22 of each link 20 is provided with a pair of wheels 32. The wheels 32 support the link 20 for movement along a conveyor track 36 (FIG. 3). A wheel 34 is positioned between the plates 26. The wheel 34 functions to center the link 20 in the conveyor track 36.
Conveyor chains of the type illustrated in FIGS. 1-3 have gained widespread acceptance in the commercial baking industry and other industries. Notwithstanding this fact, such conveyor chains incorporate various deficiencies. For example, the wheels 32 which support each link 20 for moving along the conveyor track comprise anti-friction bearings which require periodic lubrication. Lubricating the chain is time consuming and expensive, and is frequently overlooked by bakery operators. Lack of lubrication leads to bearing failure which, at a minimum, requires the conveyor to be taken out of service to facilitate replacement of the failed bearings. As will be appreciated by those skilled in the art, substantially more serious consequences can and do result from bearing failure which can require the replacement of multiple links of the conveyor chain, entire sections of the conveyor track, etc.
Various factors lead to improper conveyor chain maintenance and lubrication. One of the most important involves the demands made on commercial bakeries by their customers for continuous high level production leaving no time for maintenance and lubrication procedures. An equally important factor is the lack of technicians having the training and experience necessary to properly perform conveyor chain maintenance and lubrication procedures. When untrained and inexperienced personnel are employed to maintain and lubricate the conveyor chains used in continuous proofers and ovens, improper and inadequate maintenance and lubrication result.
A related problem attendant to the use of conveyor chains comprising links of the type shown in FIGS. 1-3 relates to the cleaning thereof. The lubricants which are used in the anti-friction bearings of the wheels 32 of the links 20 are incompatible with the use of water and detergents to clean the conveyor chain. It is therefore necessary to employ other, more costly, techniques in order to attain the level of cleanliness required in food manufacturing operations.
Even when proper lubrication and cleaning procedures are in place, the problems inherent in the use of the prior art chain are not resolved. Lubricant from the chain combines with debris from the dough products being baked to form a sludge which cannot be disposed of except pursuant to strict EPA guidelines. When the chain is used in an oven the high temperature environment causes the lubricant to thicken to the point that the bearings seize causing increased load on the conveyor drive system and increased chain and track wear.
The design of the link 20 illustrated in FIGS. 1 and 2 also involves difficulties in changing the pitch of the conveyor chain incorporating the link, that is, the distance between identical points on adjacent links. The inability to easily change the pitch of the conveyor chain in turn means that the conveyor chain cannot be readily customized to specific load profiles, for example, lengthening the pitch for light load applications and reducing the pitch for heavy load applications.
Yet another problem involves the fact that the wheels 34 positioned between the plates 26 do not restrain the links of the chain from bending and tipping. When tipping occurs, the wheels 34 act as can openers cutting slits into the side walls of the conveyor track. Tipping also tilts the grids supported on the conveyor chain which can cause displacement of the bakery pans carried by the grids.
The present invention comprises improvements in the design of conveyor chains adapted for use in conveyorized proofers, conveyorized ovens, and similar applications S which overcome the foregoing and other difficulties long since associated with the prior art. In accordance with one feature of the invention, conveyor chains intended for use in baking operations are provided with bearings which do not require lubrication. For example, when used in proofers, the bearings of the conveyor chain may comprise sleeve bearings formed from plastic materials which are self-lubricating and adapted for utilization in high temperature environments of the type encountered in a bakery oven. Conveyor chains used in ovens may be equipped with self-lubricating graphite bearings of the type sold by Graphite Metallizing Corporation of Yonkers, N.Y., under the trademark GRAPHALLOY(copyright). Alternatively, the conveyor chain may be provided with sealed self-lubricating anti-friction bearings suitable for high temperature applications.
The use of bearings which do not require lubrication in conveyor chains intended for bakery applications is advantageous for at least two reasons. First, by eliminating the lubrication function which heretofore has proven to be problematical, substantial cost savings are effected. Of equal importance is the elimination of conveyor chain failures stemming from improper lubrication. The elimination of the lubrication requirement also facilitates the cleaning of the conveyor track by simply attaching a scraper to the conveyor chain. The scraper pushes bakery debris along the track to an opening in the bottom wall thereof where the debris is accumulated for disposal as ordinary refuse.
Those skilled in the art will understand that some types of self-lubricating bearings useful in the practice of the present invention may initially have a higher coefficient of friction as compared with the anti-friction bearings currently in use. Depending on the geometries of the components, a higher coefficient of friction can result in higher loads imposed on the conveyor drive system. However, the coefficient of friction of the currently used anti-friction bearings tends to increase over time, particularly in the absence of proper lubrication. Thus, the use of self-lubricating bearings is advantageous in that the loading of the conveyor drive system remains substantially constant throughout the life of the conveyor.
Another feature of the invention comprises the use of compact carriages to support the bakery pan receiving grids. Adjacent carriages are connected one to the other by connection members which can comprise either connection rods or connecting cables. The compact carriage/connection member design is advantageous in that it is readily adapted to changes in pitch, whereby the conveyor chain in the present invention can be easily customized to a range of conveyor loading situations.
In accordance with the preferred embodiment of the invention, the conveyor chain is comprised of a plurality of identical links having spaced apart pairs of vertically disposed and horizontally disposed wheels. The diameters of the wheels are closely matched to the interior dimensions of the track whereby the wheels prevent the chain from bending or twisting. Another important feature is the fact that the chain is economical to manufacture and assemble.